Patterns of keratin polypeptides in 110 biphasic, monophasic, and poorly differentiated synovial sarcomas

Synovial sarcoma is a mesenchymal neoplasm of unknown histogenesis that shows various degrees of epithelial differentiation. It is known to contain simple epithelial keratins, and the possibility of complex epithelial keratin expression has been suggested. In this study, we immunohistochemically examined 110 well-documented synovial sarcomas including 44 biphasic, 48 monophasic, and 18 poorly differentiated (undifferentiated, highly mitotically active) tumors for 11 different keratin (K) polypeptides of the Moll catalogue. The epithelia of biphasic synovial sarcomas showed consistent, extensive reactivity for K7, K8, K14, K18, and K19. Other keratins seen in the epithelia of biphasic tumors included K17 (variable, in 77%), K13 (25%), K16 (23%), and K6 (24%) in the minority of biphasic tumors, predominantly in stratified-appearing epithelia. K10 was detected only focally in one case that showed keratinizing squamous differentiation. Focal expression of K20 was seen in 27% of cases. Monophasic synovial sarcomas had a more limited keratin repertory. Simple epithelial keratin positivity was detected, usually focally for K7 (79%), K19 (60%), K8 (45%), and K18 (46%). Two cases showed more extensive keratin positivity in the spindle cells. The monophasic tumors showed limited positivity for complex epithelial keratins: K14 (28%) and K17 (10%). K20 was detected focally in 6% of the monophasic tumors; other keratins were not detected. The poorly differentiated synovial sarcomas showed limited simple epithelial keratin reactivity, usually limited to scattered cells: K19 (61%), K7 (50%), K18 (47%), K8 (33%), but five cases showed more extensive positivity. Complex epithelial keratins were scant: K14 in one case and K17 in two cases. The immunoreactivity of capillary endothelia seen for K7 and K18 (but not for K8 and K19 with the antibodies used) is a potential diagnostic pitfall, and may cause overdiagnosis of synovial sarcoma if not properly recognized. In summary, we show complex patterns of keratins in synovial sarcoma, especially in the biphasic tumors. Such patterns establish a baseline in differential diagnostic considerations, and give an insight into the complex epithelial differentiation of this enigmatic mesenchymal tumor. Received: 17 February 2000 / Accepted: 3 April 2000     

Identification of poorly differentiated synovial sarcoma: a comparison of clinicopathological and cytogenetic features with those of typical synovial sarcoma

AIMS: Poorly differentiated areas in synovial sarcomas (SS) are known to be associated with a poorer prognosis. The aim of our study was to describe the morphological spectrum of poorly differentiated synovial sarcomas (PDSS) and refine the criteria for their recognition. METHODS AND RESULTS: The clinicopathological features of 28 PDSS were compared with those of 26 classic SS. Common cell types in PDSS included epithelioid, spindle and Ewing sarcoma-like small round cells. Unusual features included presence of desmoplastic small cell tumour-like areas and extraskeletal myxoid chondrosarcoma-like areas. The presence of necrosis (P = 0.002), a mitotic rate over 10/10 high-power fields (P < 0.001), a haemangiopericytomatous vascular pattern (P < 0.001) and vascular invasion (P = 0.003) were significantly associated with PDSS, while mast cells (P < 0.001), calcification (P < 0.001) and hyaline bands (P < 0.001) were significantly associated with classic SS. Poorly differentiated areas showed increased proliferative activity with Ki67. PDSS showed a tendency to be larger (P = 0.008) and to be located in proximal more than distal sites (P = 0.025). Three entirely poorly differentiated tumours were diagnosed by demonstration of the t(X;18)(p11;q11) translocation. PDSS showed additional cytogenetic abnormalities. CONCLUSIONS: Poorly differentiated synovial sarcomas show a spectrum of histological features, which may simulate other malignant neoplasms. The diagnosis of entirely poorly differentiated synovial sarcomas requires cytogenetic analysis.     

低分化滑膜肉瘤临床病理及分子遗传学研究

目的：研究低分化滑膜肉瘤的临床病理学特点及其分子遗传学表现。方法：收集低分化滑膜肉瘤标本121例，采用形态学观察和免疫组化染色，并用RT－PCR方法在石膜包埋组织中检测SYT－SSX融合mRNA表达。结果：12例低分化滑膜肉瘤中细胞型4例，大细胞型6例，高度恶性梭形细胞型2例。8例有随访资料其中4例死于肿瘤，平均生存时间18个月。免疫组化表现为CK和（或）EMA阳性，以EMA阳性率较高，同时vimentin阳性。S－100蛋白也有较高阳性率，多呈局灶或散在阳性。RT－PCR方法均可检测到SYT－SSXmRNA表达，对照组12例肿瘤包括恶性周围神经 鞘膜瘤、尤因肉瘤和恶性血管外皮瘤SYT－SSX检测全部阴性。结论：低分化滑膜肉瘤有其形态学及免疫表型特点，分子遗传学检测SYS－SSX融合mRNA有助于诊断和鉴别诊断。     

Cytological findings of monophasic synovial sarcoma presenting as a lung mass: report of a case and review of the literature

Synovial sarcomas are rare malignant mesenchymal tumors that can arise from any anatomic site. Although they are often located at the paraarticular region of the extremities, the incidence of synovial sarcomas in the lungs is rare, with only a few cytology case reports to date. We report a case of synovial sarcoma presenting as a lung mass diagnosed on fine‐needle aspiration (FNA) cytology. The patient is a 38‐year‐old chronic smoker who presented with cough, worsening dyspnea, and weight loss. Computerized tomography of his chest revealed an 8‐cm left lower lobe pleural‐based mass. An FNA of the lung mass showed cellular smears composed of monotonous population of singly scattered to sheets of bland spindle cells with elongated nuclei, fine chromatin pattern, and scant to moderate amount of delicate cytoplasm. Immunohistochemical stains performed on the cell block showed that the tumor cells were positive for calretinin and focally positive for pancytokeratin, CAM5.2, and smooth muscle myosin heavy chain. The tumor cells were negative for S‐100, podoplanin, and CD34. Fluorescence in situ hybridization performed on the cell block demonstrated the presence of SYT (18q11) translocation, supporting the diagnosis of synovial sarcoma.     

Pulmonary synovial sarcoma with polypoid endobronchial growth: a case report, immunohistochemical and cytogenetic study

A rare case of primary pulmonary synovial sarcoma with polypoid endobronchial growth in a 42-year-old Japanese woman is described. Left upper sleeve lobectomy was performed for the polypoid tumor measuring 2.5 cm in the left major bronchus and the patient was treated with adjuvant chemotherapy. Three years later, a recurrent tumor was discovered. Microscopically, this tumor was characterized by a proliferation of oval to spindle-shaped cells arranged in sheets and fascicles and covered by the thin normal bronchial epithelium. Immunohistochemically, tumor cells were positive for vimentin, and focally positive for pancytokeratin recognized by AE1/AE3, cytokeratin 7 and epithelial membrane antigen. A chimera gene, SYT-SSX1, was detected. Recently, primary pulmonary synovial sarcoma is an increasingly recognized clinical entity; however, most of these tumors present as a parenchymal mass. The present case is a unique example of primary synovial sarcoma of endobronchial polypoid type. This case suggests that pulmonary synovial sarcoma might originate from bronchial submucosal stromal tissue.     

Primary mesenchymal chondrosarcoma of the lung. A case report with immunohistochemical and ultrastructural studies.

A case of primary pulmonary mesenchymal chondrosarcoma is reported. The tumor occurred first in the lower lobe of the right lung of a Japanese female aged 45. Three years after the first operation it metastasized to the upper lobe of the left lung. The tumors were highly cellular and composed of undifferentiated mesenchymal cells and interspersed islands of well-differentiated cartilaginous tissue. Immunohistochemistry failed to detect S-100 and vimentin in the undifferentiated cells. In contrast, Leu-7 and blood coagulation factor XIIIa were positive in these cells. Electron microscopically, undifferentiated mesenchymal cells had narrow cytoplasm with sparsity of organelles, but no intermediate-sized filaments were detected. In the transitional areas between undifferentiated cells and cartilaginous components, thin intracytoplasmic filaments were sometimes observed in the tumor cells. The differentiation toward cartilaginous cells of undifferentiated mesenchymal cells was suggested by immunohistochemistry and electron microscopy. This is the first case of mesenchymal chondrosarcoma occurring in the lung with long-term follow-up.     

Biphasic synovial sarcoma of the abdominal wall

Synovial sarcoma arising in the abdominal wall is a rare tumor. We report a case of a 38-year-old man who complained of abdominal pain. Physical examination revealed a firm mobile mass, 25 cm in diameter, in the left lower abdominal wall. The tumor was first thought to be a sarcoma arising from the omentum or mesentery. During surgery, a large tumor was found attached to the inner surface of the abdominal wall and compressing the gastrointestinal tract. On microscopic examination the tumor corresponded to a biphasic synovial sarcoma immunoreactive for cytokeratins (AE1/AE3, 7 and 19), epithelial membrane antigen and carcinoembryonic antigen in the epithelial tumor cells, for E-cadherin especially in their glandular structure, vimentin, CD99, and CD56 in the spindle cell component and for bcl-2 protein. The tumor recurred at the same site, and clinical course progressed to death 3 months after the initial diagnosis.     

A case report of synovial sarcoma with translocation (X;18). Application of fluorescence in situ hybridization to paraffin-embedded tissue

A 57-year-old female patient with synovial sarcoma in her right foot had a chromosome abnormality defined as translocation (X;18). The tumour was located in the subcutis, and histological investigation showed monophasic proliferation of oval to spindle-shaped cells with a fascicular arrangement lacking an epithelial component. Immunostaining disclosed no cytokeratin or epithelial membrane antigen in tumour cells. Karyotypic analysis revealed translocation (X;18) in addition to other nonspecific aberrations. Fluorescence in situ hybridization was carried out on paraffin-embedded tissue, using DNA probes for the centromeres of chromosomes X and 18 with whole chromosome painting probes for X and 18. The free nuclei showed two signals at a rate of 83–85% with the X and 18 centromeric probes, in contrast to three signals at a rate of 68–70% with the X and 18 painting probes.     

Primary pleural synovial sarcoma. A case report and review of the literature

Synovial sarcoma (SS) is an uncommon soft tissue tumor that occurs primarily in the extremities of young adults, especially in the periarticular region. In this report, we describe the rare occurrence of primary SS of the pleura in a 15-year-old boy. Histologically, the tumor demonstrated monophasic morphologic findings and showed positive staining with vimentin and Bcl-2 and focally for cytokeratin CK7. Fluorescent in situ hybridization identified t(X;18) translocation. The patient developed recurrences 20 months following resection of the tumor. The literature on this uncommon entity is reviewed, and its histogenesis, differential diagnoses, and cytologic features are also discussed.